Repairable fuse with a transversely divided insulating sleeve



March 1965' H. KAMMINGA ETAL 3,174,016

REPAIRABLE FUSE WITH A TRANSVERSELY DIVIDED INSULATING SLEEVE Filed July 25. 1960 INVENTORS fill a! ATTORNEY) United States Patent M 3,174,016 REPAIRABLE FUSE WITH A TRANSVERSELY DIVIDED INSULATING SLEEVE Heiko Kamrninga and Willem Brandhorst, Hengelo, Netherlands, assignors to N.V. Fabriek van Electrische Apparaten voorheen F. Hazemeijer & (10., Hengelo, Netherlands Filed July 25, 196i), Ser. No. 45,123 Ciaims priority, application Netherlands, Aug. 1, 1959, 241,938 1 Claim. (Cl. 200-431) The invention relates to a repairable, short circuit proof fuse, comprising external contact members (in particular knife contacts) and filled with a powdered or a granular extinguishing medium, with a fuse link embedded therein.

It is common practice to use for the sleeve of the fuse a tubular element, the external circumference of which may or may not be circular, said element being made of insulating material, such as synthetic moulding resin or ceramic material.

In order to seal the end faces of the said tubular element, use is commonly made of metal end-plates, which are fastened to the tubular body by means of screws. This type of connection involves diificulties and is not altogether reliable, because screw thread is not easily made in the commonly used insulating materials, in particular ceramic materials, and in addition cannot satisfy high demands from a load point of view. This is a serious disadvantage.

A satisfactory sealing of the end faces of the sleeve is absolutely necessary in order to preclude loss of extinguishing medium. For this purpose additional plates of asbestos have been fitted underneath the said endplates.

During the operation of the fuse high internal pressures may arise. In view of this the sealing as well as the fastening of the end-plates have to satisfy special requirements.

If it is intended to repair the fuse after operation, the screwed connections of the metal end-plates have to be unscrewed at least at one of the ends and to be fixed again after the replacement of the fuse link and the refilling with extinguishing medium. There is a serious risk that after one or a few repairs the screwed connections may have been damaged so severely that the seal is no longer reliable; this is a further disadvantage.

In the constructions in question the external contact members are usually also supported by the metal endplates and are fastened to or through the latter, which necessitates additional fastening means.

Furthermore the commonly used ferro-metal endplates cause eddy current losses, resulting in an appreciable rise of temperature.

Since fuses, in particular knife fuses, are mass-produced articles, any saving of material, such as number and type of the various components, etc., will present an important economic advantage. As will appear below, such a saving is achieved by the use of the present invention.

The invention not only obviates the above-mentioned disadvantages, but also furnishes an efficient solution for satisfying the special sealing requirements.

The invention provides in an attractive way, also from the point of view of manufacture, for a repairable, short circuit proof fuse, for low voltages and relatively high currents, in which the fuse conductor is embedded in a powdered or granular extinguishing medium and fitted between flanged parts of external contact mem- 3,174,016 Patented Mar. 16, 1965 bers (in particular knife contacts) passing with an accurate fit through the end faces-which are completely closed except for openings for fastening elements to pass through and for filling the fuse--of two identical coaxially arranged one-piece cup-shaped sleeve elements, clamped together along a plane of division transverse to the longitudinal axis of the fuse, said sleeve elements being made of insulating synthetic material (e.g. on a synthetic resin base) and having elements integral therewith and adapted to accommodate known fastening means, the flanged parts of the contact members closely fitting the inside of the end faces of the sleeve elements and containing or supporting means for accommodating said fastening means, the sleeve elements having been moulded to be removed from the mould in a direction opposite to the pressing direction.

Although a division along a transverse plane at any given angle will yield a cup-shaped sleeve element that can be moulded in one single direction, a division along a transverse plane at right angles to the longitudinal axis of the cup-shaped sleeve element is preferred.

The invention will be explained more fully below with reference to the drawing, which illustrates an embodiment by way of example.

The single figure is a perspective view partly in section of the fuse assembly of the invention.

The short circuit proof knife fuse shown in the drawing consists of two identical cup-shaped sleeve elements 1, of insulating material, which are fastened together coaxially. They contain two fuse links 2, connected firmly and conductively to flat flanged parts 3 of knife contacts 4.

Each of the sleeve elements 1 is made of an insulating synthetic moulding resin and has been moulded to be removed from the mould in the direction opposite to the pressing direction. In the otherwise completely closed end face of each of the sleeve elements 1 a number of openings are made during the moulding process. In the first place, a slot-shaped opening, for the knife of the knife contact 4 to pass through with an accurate fit. In the second place, twoopenings accommodating fastening screws 5 for the knife contacts 4. And in the third place, an opening 6 for filling the fuse with sand and for accommodating an indicator, if desired.

The other end of each circular sleeve element 1 is in the form of a square flange 7 with rounded corners, also at right angles to the longitudinal axis of the sleeve element. Arranged symmetrically at the four corners are countersunk holes 8 and continuous holes 9.

The basic element of the repairable fuse under consideration is the unit comprising the two knife contacts 4 and the fuse links 2 connected therebetween. One of the cup-shaped sleeve elements 1 is pushed over each of the contact knives until it rests against the flanged part 3. By means of the fastening screws 5 the flanged part 3 is drawn close against the flat inside of the sleeve element. To this end the flanged part 3 is provided with screwed holes. At the same time said flanged part 3 provides a satisfactory seal against the end face of the sleeve element. By means of screws 10 and nuts 11 the flat faces of the flanges are pulled against one another and thereby sealed.

The invention is not restricted to the embodiment described above.

What we claim is:

A repairable fuse comprising in combination, a housing consisting of a pair of identical one piece cup shaped sleeve elements of insulating material having a slot shaped aperture in one end thereof opposite a sealing flange thereon at the other end, removable clamping elements holding the flanges together along a plane of division transverse to the longitudinal axis of the fuse to form a housing which may be disassembled during repair of the fuse, a pair of contacts having straight knife blades which register with said apertures and extend from a flanged part, removable mounting means adjacent said slotted apertures in said sleeve elements affixing said contact flanges Within said housing with the knife contacts extending through said apertures in sealing relationship terminated with the flanged portion positioned adjacent the interior surface of the end Wall of each cup to thereby permit removal of said knife contact from said sleeve through said aperture upon disassembiy of the fuse for repair, and a fuse link connecting the flanged portions of said knife contacts.

References titted by the Examiner UNITED STATES PATENTS Brach 200118 Thomas ZOO-115.5 Frank.

Matthysse.

Breisch et a1.

Moeller 200-131 Swain 200131 Swain et al 20013l Great Britain.

RICHARD 

